062022
562
23012022
15042022
R.S. Herrera
Instituto de Ciencia Animal, Cuba
Abstract: A three-year experiment was carried out to evaluate the agronomic performance of new varieties of Cenchrus purpureus (CT-600, CT-601, CT-602, CT-603, CT-605, CT-607, CT-608 and CT -609), tolerant to drought, obtained by in vitro tissue culture, and compared with its parent (CT-115) through a completely random design with five replications. There were significant differences between the height of the varieties and in both seasonal periods CT-605 stood out with values higher (P<0.05) at 90 cm. The leaves content (%) was only significantly different between the varieties in the dry season during the experimental stage, while the percentage of stems showed a similar response pattern. There were varieties that exceeded the DM yield of the control and especially the CT-605 with values of 21.82, 16.37 and 9.05 t DM/ha/year for the first, second and third year, respectively. With the exception of the first year, the varieties did not express their potential for biomass production under water stress conditions and future researches are suggested where rainfalls is less than 800 mm, as well as studying the effect of strategic fertilization on regimes of greater rainfall.
Key words: water stress, tolerance, yields, population.
Resumen: Se realizó un experimento de tres años de duración para evaluar el comportamiento agronómico de nuevas variedades de Cenchrus purpureus (CT-600, CT-601, CT-602, CT-603, CT-605, CT-607, CT-608 y CT-609), tolerantes a la sequía, obtenidas por cultivo de tejidos in vitro, y compararlas con su progenitor (CT-115) mediante un diseño completamente al azar con cinco réplicas. Hubo diferencias significativas entre la altura de las variedades y en ambos períodos estacionales sobresalió CT-605 con valores superiores (P<0.05) a los 90 cm. El contenido de hojas (%) solo fue significativamente diferente entre las variedades en el período poco lluvioso durante la etapa experimental, mientras que el por ciento de tallos mostró similar patrón de respuesta. Hubo variedades que superaron el rendimiento de MS del testigo y en especial la CT-605 con valores de 21.82, 16.37 y 9.05 t MS/ha/año para el primer, segundo y tercer año, respectivamente. Con excepción del primer año, las variedades no expresaron su potencial para la producción de biomasa en condiciones de estrés hídrico y se sugiere futuras investigaciones donde las precipitaciones sean inferiores a los 800 mm así como, estudiar el efecto de la fertilización estratégica en regímenes de mayor precipitación.
Palabras clave: estrés hídrico, tolerancia, rendimientos, población.
Pasture Science and other Crops
Evaluation of Cenchrus purpureus varieties tolerant to drought in the western region of Cuba
Evaluación de variedades de Cenchrus purpureus tolerantes a la sequía en la región occidental de Cuba
R.S. Herrera
Received: 23 January 2022
Accepted: 15 April 2022
Africa is the center of origin of Cenchrus genus, previously called Pennisetum, and its varieties (Cenchrus purpureus) are widely used for the production of animal food, mainly as forage (Pereira et al. 2017) or through direct grazing (Gomide et al. 2011). This is determined by its high capacity to use light energy, carrier of the C4 photosynthetic cycle, high DM yields, acceptable quality (Coombs et al. 1973) and it adapts, grows and develops in a wide variety of soils and climatic conditions (Febles and Herrera 2015). In addition, it can be used for other purposes, such as: production of energy (Chakraborty et al. 2012) and bioethanol (Santos et al. 2018), paper industry (Madakadze et al. 2010) and natural herbicide (Norhafizah et al. 2013).
Different varieties have been used in Cuba since the beginning of the 20th century, such as the Napier, which spread throughout the country very quickly due, among other factors, to its high yields and acceptable chemical composition. Subsequently, other varieties were introduced, one of which was the King grass, which in the mid-1980s occupied 85% of the country's forage areas and displaced those traditionally used, which was determined for its high capacity to convert light energy into biomass, its ecological plasticity, high biomass yields and adequate quality (Herrera 2009).
On the other hand, due to the importance achieved by this genus, genetic improvement programs are developed (Sinche et al. 2021) with the objective of obtaining varieties that surpass those traditionally used. Also, at the Instituto de Ciencia Animal, a breeding program for C. purpureus was developed with the aim of improving the productive indicators of the most used variety (King grass), in commercial production and adapting to current climatic and soil conditions, including varieties tolerant to drought and salinity (Herrera 2020).
Due to the above, the objective of this article is to report the results achieved in the evaluation of Cenchrus purpureus varieties obtained by in vitro tissue culture tolerant to drought.
Location. the experiment was carried out at the Miguel Sistachs Naya pasture station belonging to Instituto de Ciencia Animal. The soil was Typical Red Ferralitic (Hernández et al. 2015) whose chemical composition appears in table 1 and some climate indicators are shown in the table 2.
Treatment and design. A total of eight new Cenchrus purpureus varieties (CT-600, CT-601, CT-602, CT-603, CT-605, CT-607, CT-608 and CT-609) obtained at Instituto de Ciencia Anima were evaluated by in vitro tissues culture with tolerance to drought (Herrera et al. 2003), from Cuba CT-115 variety, which was used as a control. A random block design with four replications in 5 x 4 m plots was used.
Procedure. During the dry season, conventional soil preparation was carried out and a distance of 1m between rows was used. In the planting, a similar number of buds per row were ensured. Irrigation was applied at the time of planting and three times later to ensure adequate humidity and establishment. One hundred and twenty days after sowing, the establishment cut was made to start the evaluation process without the application of irrigation or fertilization. The experiment lasted three years.
Measurements. Sampling was carried out every 60 and 90 days in the rainy and dry seasons, respectively, where five tillers were taken per row in each replication to determine: plant height considered from the base to the apical cone, percentage of leaves and stems, DM yield and population as described by Herrera (2006).
Statistical analysis. The database was created and analysis of variance was performed (Di Rienzo et al. 2012) according to the experimental design and the mean values were compared according to Duncan (1955). The theoretical assumptions of the analysis of variance were verified for all the variables, based on the Shapiro and Wilk (1965) tests for the normality of errors and Levene (1960) for the variance homogeneity and there was only the need to transform the population variable using √x.
Throughout the experimental stage, there were significant differences between the varieties in each climatic season for height (table 3). This is an indicator that expresses the plant growth in response to environmental conditions (climate and soil) and the management to which they are subjected. This could be determined by the biochemical and physiological particularities of each variety (Sinche et al. 2021) and, therefore, they will show better growth under conditions of humidity or rainfalls stress, an aspect that does not happen in the rainy season, where the climatic factors such as rainfalls, temperatures, intensity and duration of light, among other aspects, do not limit the growth and development of grasses.
On the other hand, Guimaraes de Favare et al. (2019) when evaluating 13 varieties of Cenchrus purpureus for bioenergy production found that the height did not differ between them in the dry period and there were differences in the rainy period in both experimental years, but in the second year the height was lower. A similar pattern of performance was previously reported by Herrera and Ramos (2015). However, it was encouraging in this research that, after three years of study, there was no decrease in height, which could be a reflection of its adaptation to the environment despite not using irrigation and nitrogen fertilization.
During the rainy season there was no variation in leaves content between the varieties in the three years studied. However, in the dry season of the first year, only CT-603 exceeded (P<0.001) the control (CT-115), while in the same period of the third year none exceeded CT-115 (table 4). This drew attention, since the response pattern varied over the years. However, the values recorded in the rainy period were encouraging despite the values recorded for rainfalls while, in the third year of study, with the exception of CT-603, all varieties showed higher leaves content compared to the first year. This performance should be studied in future experiments due to the role that leaves play in the Physiology and Biochemistry of plants. On the other hand, leaves content is a fundamental element for ruminants feeding, since it is the part most intake by animals, so it is an important element when selecting new varieties.
Reyes-Perez et al. (2021) when evaluating five varieties of C. purpureus (Verde, Morado, Maralfalfa, CT-115 and Elefante) in Ecuador, found that leaves yield increased with fertilization and regrowth age and each variety showed a characteristic response pattern. Tulu et al. (2022) studied the effect of the year, the date and the cutting height in Napier and determined that the leaf/stem ratio decreased with the years of study and the cutting height, while the cutting date (month) had a varied effect. The mentioned authors relate these results to the performance of climatic factors, the plant age, the type of soil and the management of grass, among other aspects.
The stem content (table 5) showed an inverse performance to that mentioned above. However, this aspect can be unfavorable from the point of view of animal intake , since they, in the process of selecting food, first intake the leaves and ultimately the stems, but from the point of view of Plant Physiology, they favor the storage of soluble carbohydrates, especially in the lower parts of the stem, to facilitate the plant regrowth even in the absence of sufficient leaf area and, in addition, it allows the storage of appreciable amounts of water, which guarantees the metabolism and plant survival under stress conditions.
On the other hand, Arias et al. (2018, 2019ab) when evaluating some of the drought-tolerant varieties of C. purpureus (CT-601, CT-603, CT-605, CT-608 and CT-609) in the eastern region of the country, showed that the regrowth age increased the length, thickness and number of stem nodes, being these responses specific for each variety.
With the exception of the dry season of the first year, there were differences between varieties in yield for each seasonal period and for the annual total (table 6). The absence of differences in the first year of exploitation in the dry season is not easy to explain, especially if it is takes into account that in the rainy season there was. In the second year, in this same period, there were differences and the values tended to be lower when compared to the first year, which could be determined by the decrease in soil fertility due to the extraction of mineral elements that these plants make, especially nitrogen and potassium. This could be an indicator to carry out a strategic or maintenance fertilization using chemical fertilizers (if available) or organic from the second year of exploitation. The lowest values were recorded in the third year.
Reyes et al. (2021) found in four varieties of C. purpureus that the yield of green biomass and dry matter increased with fertilization and age. Sinche et al. (2021), when evaluating a population of Napier hybrids, found that indicators such as height, stem diameter, flowering, and yield varied among the hybrids. Ventra Rios et al. (2022), when they studied the response of Taiwan (C. purpureus) grass to cutting frequency, reported that yields increased with the regrowth age. Arias et al. (2019a) when evaluating some of the drought-tolerant varieties in the eastern region of Cuba reported increases in yields with the regrowth age. All this information has in common the specific and individual response of each of the studied plants.
All of the above is confirmed by the results published by Arias et al. (2019b) when studying physiological indicators such as absolute and relative growth rate, leaf area and leaf area index, leaf area duration and biomass duration in C. purpureus varieties with drought tolerance. The six varieties showed values that individually characterized each of them and confirmed their biochemical and physiological individuality.
In the evaluated period (table 7), there were no significant differences for the population of the varieties and the values at the end of the experiment were similar to those registered in the first year, since the varieties did not suffer depopulation. This is positive if it is taking into account that during the three years of research both irrigation and fertilization was used.
These varieties were evaluated (Díaz 2007, Arias et al. 2018, 2019ab and Ray et al. 2018) in the pasture station of Instituto de Investigaciones Agropecuarias Jorge Dimitrov, located in Cauto Valley, Bayamo, Granma and that area is characterized by soils with low fertility and rainfalls regimes that reach 700-800 mm of rain and drought periods that extend up to seven months). The results showed the adaptability of the varieties and, above all, the yields achieved in the dry season, where rainfalls did not exceed 50mm, so their performance against drought stress is unquestionable. In addition, promising results were obtained when evaluating the ruminal passage rate and ruminal degradability of these varieties (Ledea et al. 2016, 2017).
However, this was not the response found in the varieties in this study, which was determined by the high rainfalls that occurred in the second and third year of research (table 2), which limited the plants from expressing their production potential under drought stress conditions. However, in the first year of research, the value of rainfalls was lower than the rest of the experimental years and below the historical value, which could influence on the yields obtained that year. The previous determines the need to carry out future researches under of water stress conditions, as well as to use strategic fertilization in the rainy season in the western region of Cuba.
Thanks to the technicians M. García and Ana M. Cruz for their attention to the experiment, the sampling, the processing of samples and the analysis of the results.
*Email: rsherrera48@gmail.com
